Chromatography columns may be used in industrial processes to purify process liquids and separate substances of interest from process liquids; typical examples include large-scale preparative purification of fine chemicals and pharmaceuticals, together with biological products. Industrial-scale chromatography columns typically comprise a hollow, axially vertical tubular housing or tube including a liquid inlet at the upper end or lower end and through which the buffer and substances to be separated are dispensed to the media bed located within the cavity of the tube, and a liquid collecting system at the other end for collecting substances and buffer. The particulate chromatographic media or bed through which the buffer fluid and/or substances to be separated and purified percolates is located between the liquid inlet and collecting system. An adapter assembly is typically affixed to the upper end of the tubular housing and a base assembly to the lower end where it is bolted to the bottom flanges. Each of these assemblies typically comprises a strong backing plate and a distributor which further supports a bed support: a bed support is a layer of mesh, filter, sinter, screen or other fluid-permeable media-retaining material which permits process liquid flow into and out of the chromatography bed space or cavity while retaining the bed of particulate medium. To provide adjustability and control of the bed height and bed compression, the adapter assembly is typically made in the form of a piston or sliding adapter in the column tube interior. After the column is charged with bed media, typically through a nozzle, the adapter may be forced toward the bottom of the tube to compress or pressurize the media bed. Generally the base assembly is a fixed structure which is bolted against the bottom flange of the column tube but, in some instances, may also be in the form of a movably slidable piston or adapter.
The backing plate of the base assembly generally acts as a support for the column, being itself supported on legs or some other stand arrangement which allows clearance for outlet pipe work projecting beneath the base assembly. However, in some columns clearance may not be sufficient for easy maintenance.
Prior art adapter and base assemblies are formed by screwing or bolting the distributor plate into the backing plate by means of bolts or screws. As the distributor is made of inert nonmetallic materials, such as plastic, it may become distorted during the operation of the column when it is subjected to internal pressures ranging from −1 bar to +5 bar. To overcome this problem, the distributor is secured to the backing plate with many screws or bolts. This process typically requires helicoil threads being cut into the distributor plate, a process that can be costly and difficult to implement in high quality materials like stainless steel, polypropylene and other materials which are suitable for use in a GMP environment, and securing the distributor to the backing plate using appropriately threaded screws or bolts.
A significant number of such bolts or screws are required (e.g. in 1 meter diameter column there would typically 20 to 40 screws or bolts and for a 2 meter diameter column approximately 100 to 150 screws or bolts) to secure the distributor to the backing plate as the resulting assembly must be able to withstand back compression pressures when, for instance, the column is being packed. The process of securing the distributor plate to the backing plate by the use of screws and/or bolts can be time consuming when the chromatography column is initially being set up for operation. Errors may occur in the set up process when screws or bolts of the wrong length or incorrect bore are used, resulting in a weaker seal between the component parts.
Corrosion of the screws or bolts, and of the screw threads, can occur with time and repeated use of the column. Furthermore, the cleaning and/or maintenance of the column often necessitates the separation of the distributor plate from the backing plate. Once again, this process requires time to carefully unscrew or unbolt the distributor from the backing plate.
There is therefore a need for chromatography columns which have a simpler, cost-effective means of securing the distributor plate to the backing plate to overcome the above mentioned problems encountered in the prior art.